Slur and carrier drive mechanisms for fully fashioned flat bar knitting machines

ABSTRACT

STRAIGHT-BAR KNITTING MACHINE HAVING A YARN CARRIER DRIVE DRIVEN FROM VARIABLE DRAW MECHANISM OVER MINIMUM DISTANCES ONLY SLIGHTLY IN EXCESS OF THOSE REQUIRED FOR CARRIERS TO TRAVERSE THE KNITTING WIDTH IN EITHER DIRECTION, AND A DIFFERENTIAL IS PROVIDED FOR IMPARTING AN EXTRA LINEAR MOVEMENT TO A SLUR CAM BOX TIE BAR EACH TIME THE CARRIER ROD IS ARRESTED BY A STOP, THEREBY ACHIEVING A LEAD OF THE CARRIERS AHEAD OF THE SLUR CAMS. THE DIFFEENTIAL PREFERABLY INCLUDES A CHAIN SPROCKET WHICH IS ENGAGED WITH A SLUR DRAW CHAIN AND IS SECURED UPON A SHAFT TO WHICH IS ALSO SECURED A PINION ARRANGED IN MESH WITH A SLUR DRIVE RACK. THIS SHAFT TURNS IN A GUIDED SLIPPER CONNECTED WITH LEAD CHANGEOVER MEANS.

Feb. 16, 1971 E. WEST ETAL I 3,563,062

SLUR AND CARRIER DRIVE MECHANISMS FOR FULLY FASHIONED FLAT BAR KNITTING MACHINES Filed July 14, 1969 5 Sheets-Sheet 1 Feb. 16, 1971 5, WEST ET AL SLUR AND CARRIER DRIVE MECHANISMS FOR FULLY FASHIONED FLAT BAR KNITTING MACHINES 5 Sheets-Sheet 2 Filed July 14, 1969 a up Feb. 16, 1971 E. WEST ET AL 3,563,062

SLUR AND CARRIER DRIVE MECHANISMS FOR FULLY FASHIONED FLAT BAR KNITTING MACHINES I Filed July 14, 1969 5 Sheets-Sheet 5 Feb. 16,1971

E. WEST ET AL SLUR AND CARRIER DRIVE MECHANISMS FOR FULLY FASHIONED FLAT BAR KNITTING MACHINES Filed July 14, 1969 5 Sheets-Shoot vc G Feb. 16, 1971 WEST ET AL 3,563,062

SLUR AND CARRIER DRIVE MECHANISMS FOR FULLY FASHIONED FLAT BAR KNITTING MACHINES Filed July 14, 1969 5 Sheets-Sheet 5 SCV &

United States Patent 3,563,062 SLUR AND CARRIER DRIVE MECHANISMS FOR FULLY FASHIONED FLAT BAR KNIT- TING MACHINES Ernest West, Kirkby-in-Ashfield, and Frederick R. Challenger, Loughborough, England, assignors to S. A. Monk (Sutton-in-Ashfield) Limited, Sutton-in-Ashfield, England, a British company Filed July 14, 1969, Ser. No. 841,453 Claims priority, application Great Britain, July 20, 1968, 34,743/ 68 Int. Cl. 15/52 US. Cl. 66-126 Claims ABSTRACT OF THE DISCLOSURE Straight-bar knitting machine having a yarn carrier drive driven from variable draw mechanism over minimum distances only slightly in excess of those required for carriers to traverse the knitting width in either direction, and a differential is provided for imparting an extra linear movement to a slur cam box tie bar each time the carrier rod is arrested by a stop, thereby achieving a lead of the carriers ahead of the slur cams. The differential preferably includes a chain sprocket which is engaged with a slur draw chain and is secured upon a shaft to which is also secured a pinion arranged in mesh with a slur drive rack. This shaft turns in a guided slipper connected with lead changeover means.

This invention relates to mechanism for driving the slur cams and yarn carriers in a multi-head straight bar knitting machine of the Cottons patent or similar type for fully-fashioned garment manufacture.

In a machine of the type concerned, slur cams, one to each head or division, are mounted in slur cam boxes fastened to a tie bar which extends along the length of the machine and thereby couples the slur cam boxes together. Thus, driven from the main draw mechanism, the tie bar drives the slur cams across the sinker heads at the divisions. The said tie bar is associated with a fixed slur bar or rail which, in the case of a machine fitted, as is the machine to which the invention is applied, with a variable draw mechanism, is mounted on small levers to enable the said slur cams to be retracted from the rear of the sinker heads during the knitting part of the loop forming cycle.

Associated with the slur cams which, together with sinkers they operate, perform the yarn sinking function, is or are a rod or rods which or each of which extends the length of the machine and upon which are mounted yarn carriers, at least one to each sinker head. The requirement is that a carrier rod shall synchronously reciprocate with the slur cams on all knitting widths but with a controlled lead of the said carriers over the slut cams. That is to say, each slur cam travels a substantially constant distance beyond the yarn carrier selvedge positions at the relevant head or division.

The invention is primarily intended for application to a machine having a chain type of yarn carrier drive combined with means to give the necessary controlled lead of the yarn carriers ahead of the slur cams during each traverse. It is, however, also possible to apply the invention to a machine equipped with a friction type of yarn carrier drive, as will be hereinafter more fully described.

The invention, moreover, has reference exclusively to a multi-head straight-bar knitting machine of the type specified including any appropriate means for shaping knitted fabric or garment blanks produced at the divisions. In this case, the increase or decrease in the knitting width ice in controlled by conventional L.H. and RH. selvedge screws which are indexed according to a machine control system capable of being programmed according to the garment shape specification. These selvedge screws limit the traverses of the yarn carrier rod or rods, which or each of which, or a component connected thereto contacts stops movable together with nut housings on the selvedge screws. Similarly, these selvedge screws also effectively vary the traverses of the slur cams according to the knitting width by means of the proportional movement of die blocks in a reciprocating linkage actuated from the draw mechanism which is of the kind in which a rotary draw cam, operating on trucks mounted on a pitman to cause to and fro movement of the latter, is used to effect, through the medium of a swinging lever system and associated transmission, variable reciprocating motion to the slur cams and carriers.

As is well known to those acquainted with the art concerned, a straight-bar knitting machine of the type referred to is provided with a continuously rotatable cam shaft from and by which the various machine motions are respectively derived and controlled. From this cam shaft is driven, usually through the medium of 2:1 bevel gearing, a cross shaft upon which is secured the aforementioned rotary draw cam.

Heretofore, on this type of knitting machine it has been the practice to drive the tie bar appreciable distances beyond the selvedge positions of the yarn carriers from the rotary draw cam, through the medium of the pitman, the swinging lever system and racks and pinions. Thus, since each carrier must move at the same speed and in the same direction as the relevant slur cam, but at a distance in advance of it constituting the aforementioned lead, it follows that the carrier driving member (of a chain or a friction drive) must also, in the prior arrangement, travel the same distance. Overtravel of the carrier driving member has previously been relied on to produce the lead of the carrier in front of the slur cam, such overtravel being permitted by an escapement on a carrier driving chain or slip of the frictions in the case of a friction carrier drive. In such an arrangement, a yarn carrier reaches a stop (at the termination of a traverse in either direction) while moving at a relatively high velocity and so causes high impact forces to be developed. In practice this has been found to be one of the factors which limits the maximum speed of the machine, due to precise control of the carriers being very difficult to achieve under high impact conditions.

The primary object of the present invention is to make possible a substantial reduction in the velocity of the yarn carriers as they reach their stops.

According to this invention, the yarn carrier driving means are arranged to be driven from the variable draw mechanism distances only slightly in excess of those required for carriers on a rod to traverse the knitting width in either direction, and for the purpose of achieving the lead of the carriers ahead of the slur cams means are provided for imparting an extra linear movement to the tie bar each time the carrier rod, or a component connected thereto, comes up against and is arrested by a stop.

The extent of each traverse of the reciprocable carrier rod is kept to a minimum which is a substantially constant but not necessarily consistent amount in excess of the actual knitting width which latter, however, is always a precise distance. The carrier rod traverses are controlled from a primary cam constituted by the aforementioned rotary draw cam.

The means employed to impart the extra linear movement to the tie bar each time the carrier rod is arrested 0 by a stop may conveniently consist of a linear differential adapted to be reciprocated to and fro under the control of a secondary cam suitably timed in relation to the primary cam. Such a linear differential may include sprockets and a chain or chains, although toothed racks and pinions may alternatively be employed.

The invention is not, however, necessarily confined to a linear differential as it would also be possible to adopt a differential gear gear box incorporating intermeshed toothed rotary gears.

In any event, two inputs derived from the variable draw mechanism and so arranged as to be additive relatively to one another are applied by the differential, whatever, its form, to influence an output which functions to achieve the additional and substantially constant overtravel of the slur cams.

The traverses of the yarn carriers are such that their peak velocities are minimised, thereby reducing the decelerating forces and impacting whenever a carrier rod is brought to rest.

A further object of the invention is to provide, in a straight bar knitting machine of the type concerned furnished with a differential as and for the purpose hereinbefore described, an overload protection which, if excessive overload occurs, will cause the slur and/or the carrier drive or drives to be disconnected automatically and to stop the machine, thus preventing damage to the machine.

The overload protection may be provided by a torque limiting device which is incorporated in the transmission between the variable draw mechanism and the carrier and slur drives so that any malfunction or overload of the said mechanism will cause the device to disengage without damage.

An overload condition may cause a displacement of one of the members of the torque limiting device as the drive is disengaged, and this displacementt may be utilised to effect operation of any appropriate switch by means of which the machine is caused to stop. It is essential that when the overload device is disengaged it shall be re-engaged by a manual resetting operation after the machine has stopped.

In order that the invention may be more clearly understood and readily carried into practical effect, one specific form of linear differential mechanism for imparting additional and substantially constant overtravel of slur cams beyond the selvedge positions of corresponding yarn carriers and also comparative graphs illustrating slur and carrier travel and velocity as met with respectively in a prior art machine and an improved machine embodying the present invention will now be described with reference to the accompanying drawings, wherein,

FIG. 1 illustrates so much of a straight bar knitting machine of the type concerned, as viewed from the rear, as is necessary to illustrate in purely diagrammatic fashion, a chain type carrier drive, a slur drive, a variable draw mechanism from which these drives are driven, the aforesaid linear differential and an associated lead changeover mechanism,

FIG. 2 shows the variable draw mechanism in detail,

FIG. 3 is an elevational view of the linear differential,

FIG. 4 is a part-sectional view illustrating an overload (torque limiting) device which is arranged in the drive transmission between the variable draw mechanism and the carrier and slur drives,

FIG. 5 is a cross-sectional view of the said device when driving,

FIG. 6 is a similar view to FIG. 5 but showing the torque limiting device disengaged,

FIG. 7 shows related graphs of slur and carrier travel and velocity as in a prior art machine, and

FIG. 8 are similar graphs showing, by way of comparison, the slur and carrier travel and velocity as in a machine improved by the incorporation therein of the differential of this invention.

Like parts are designated by similar reference characters throughout the drawings.

Referring to FIG. 1, parts of which are in exploded form in the interests of clarity, it will be seen that the machine is provided, at each head or division, with a yarn carrier YC secured to a reciprocable rod 1 and a slur cam SC which is mounted in a slur cam box 2 fastened to a linearly movable tie bar 3. The carrier rod 1 is required to reciprocate synchronously with the tie bar 3 on all knitting widths, such as KW, but with a controlled lead CL of the carriers over the slur cams.

The tie bar 3 in the illustrated example is driven to and fro from the main rack 4 of the variable draw mechanism VDM of the machine-through the medium of a pinion 5 mounted on a shaft 6; a triple slur-draw chain 7 passed around triple chain sprockets 8 and 9 of which the latter is also secured upon the shaft 6; a pinion 10 secured upon a further shaft 11 to which is also secured another triple chain sprocket 12 arranged in mesh with the lower run of the chain 7; and a slur drive rack 13 which is mounted on and rigid with the tiebar and has the pinion 10 arranged in mesh therewith.

The sprocket K12 constitutes a part of the linear differential by means of which the additional and substantially constant overtravel of the slur cams such as SC is achieved, as will be hereinafter more fully described.

The diagrammatically illustrated machine is equipped with a chain type carrier drive a double carrier driving chain of which is indicated at 14. This chain is driven to and fro from the main raok 4 through the medium of a double chain sprocket 15 which is secured upon the end of the shaft 6 remote from the pinion 5.

As to the variable draw mechanism VDM, this is of the general character disclosed in the Complete Specification of our prior United Kingdom Letters Patent No. 778,472. Thus, the said mechanism includes a rotary draw cam 16 which, as shown in FIGS. 1 and 2, is mounted upon the conventional cross shaft :17 adapted to be driven from the main camshaft of the machine through the medium of 2:1 bevel gear and pinion. This draw cam, operating on trucks 1'8 and I19 mounted on a pitman lever 20 cause the latter to oscillate to and fro between a short draw lever 21 and the supporting lever 22. The short draw lever 21 acts as an intermediate lever between the fixed throw of the pitman lever 20 and the variable throw of the main draw lever '23. The connection between the draw levers 21 and 23 is obtained by a connecting pin 24 which connects together two sliding die blocks 25 and 26. The die block 25 operates in a slot 27 in the short draw lever 21, and the die block 26 operates on a lead screw 28. With the connection between the two draw levers as shown, the main draw lever 23- will operate over the full needle bar width. When the knitting width KW is varied the selvedge screw 29, functioning together with the L.H. selvedge screw 30, to control the positions of carrier stops 31 and 32 (and hence also the knitting width), is rotated and the motion thereof is transmitted to a short driving shaft 33 via two sprocket wheels 34 and 3 5 and a chain 36 passed around them, all as shown in FIG. 2. The sprocket wheels 34 and 35 are mounted on the rR.H. selvedge screw 29 and the driving shaft 33 respectively. The motion is thereupon conveyed to the draw lever lead screw 28 by two bevel gears 37 and 38 acting on a universal joint 39. Thus, for instance, as the knitting width decreases, the lead screw 28 is rotated and the die block 2 6 moved away from the universal joint 39 which forms the fulcrum of the main draw lever 23- an action which results in a reduction of the stroke of the said draw lever. The drive from the main draw lever 23 to the main rack 4 is through a pin 40 and a die block 41 operating in a slot cut in the upper end of 23.

The carrier driving chain 14 is furnished with a. roller 42 (FIG. 1) which serves to drive a carrier driving slide 43 to and fro between conventional saddles 44 and 45. For each oscillation of the draw lever 23 the driving roller 42 passes around two pairs of sprocket wheels 46, 47 and 48, 49 on the two saddles 44 and 45 respectively.

The said saddles (which carry the carrier stops 31 and 32 arranged to be contacted by opposite ends of the carrier driving slide 43) are mounted for sliding movement on a guide bar 50 and are connected to nut housings 51 and 52 engaged with the RH. and L.H. selvedge screws 29 and 30 respectively. The knitting width KW is the distance between the centre lines of the two pairs of sprocket wheels 46, 47 and 48, 49. The carrier driving slide 43 is mounted for sliding movement on a horizontal guide bar (not shown) disposed at the backs of the saddles 44 and 45. There is a mechanical connection, diagrammatically represented by the chain line 53 in FIG. 1, between the carrier driving slide 43- and the carrier rod :1 whereby each yarn carrier YC on this rod is driven to and fro across the sinker head at the relevant division, the ends of the carrier traverses being determined by contact of the ends of the slide 43 with the stops 31 and 32. Although in the exploded upper portion of FIG. 1 the carrier rod 1 is, for clarity, depicted as being above the carrier driving slide 43, it is to be understood that in practice this rod would be disposed beneath the said slide. The roller 42 operates between two spring loaded plungers 54 and 55 of the carrier driving slide. The drive is discontinued as the roller 41 moves out of its driving position either downwards around the sprocket wheel 48 or upwards around the sprocket wheel 46. The vertical movements of the roller 42 and chain 14 at these points takes the roller out of contact with the plungers 54 and 55.

As will be appreciated from the foregoing description, longitudinal movement of the slur-draw chain 7 is transmitted to the slur drive rack 13 through the medium of the chain sprocket 12 and the spur pinion 10both secured upon the shaft 11. The latter is mounted to turn in a boss-like bearing 56a of a slipper 56 which is displaceable leftwards and rightwards along a guide rod 57. Idler sprockets 58 and 59 maintain engagement of the slur-draw chain 7 with the sprocket 12, these idler sprockets being free to rotate about their own axles 60 and '61 set in the slipper 6.

The sprocket 8 is a guide sprocket which is mounted on a bracket (not shown) secured to the framework of the machine.

The slipper 56 is connected, through the medium of a link 62, with a lead changeover mechanism diagrammatically depicted at LCM in FIG. 1. Some automatically operable lead changeover means are necessary in the illustrated example (including a carrier driving chain) to reverse the controlled lead of each yarn carrier such as YC over the corresponding slur cam SC at each reversal of the traverse of the slur cam across the relevant sinker head. The particular mechanism LCM shown at the bottom right-hand of FIG. 1 functions to shift the slur drive rack 13 an appropriate distance, in the relevant direction and relatively to the carrier driving chain 14, at each reversal of slur traverse-through the medium of the link 62 and the pinion 10. Thus, LCM comprises a relatively long pivoted lever 63 to which the appropriate end of the link 62 is attached and a substantially shorter lever 64, the said two levers, arranged parallel to one another, being connected by a pitman 65. The pitman 65 carries two trucks 66 arranged in contact with respectively opposite sides of a rotary lead cam 68 rigidly secured either upon the cross shaft '17 (as shown) or upon any other suitable half-speed shaft. As the cam 68 rotates, the slipper 56 will be moved to and fro in time with reversals of the slur traverse. At each such reversal, displacement of the slipper 5 6 causes the chain sprocket 12 and hence also the pinion to rotate suchwise as to shift the slur drive rack 13 and thereby change over the lead.

The movements imparted to the sprocket are sufficient to drive each yarn carrier YC, through the chain 14, from one selvedge position to the other across the knitting width KW-with a slight overtravel which is permitted by the shape of the chain path, or by the slipping of frictions in the case of a friction type carrier drive. During this period the lead cam 68 imparts no movement to the slipper 56 due to the fact that the relevant lead truck 66 is on a run portion of the cam 68. The linkage consisting of the pitman 65, the lever 63 and the link 62, and hence also the slipper 56, are therefore stationary but, due to the rotation of the pinion 5 by the variable draw mechanism VDM operated from the rotary draw cam 16, the slur-draw chain 7 is driven from the sprocket 9 and so causes the sprocket 12 of the linear differential to rotate. Such rotation of the said sprocket 12, and hence also of the shaft 11 which is free to rotate in the slipper 56, causes the pinion 10 to drive the slur drive rack :13 so that the slur cam boxes 2 are also driven through the medium of the tie bar 3.

However, further rotation of the cross shaft 17 causes the slipper 56 to be displaced along the guide rod 57 due to the action of the lift portion of the lead cam 68 activating the linkage 66, 65, 63 and 62. This displacement of the slipper relatively to the slur-draw chain 7 effects further rotation of the sprocket 12 and shaft 11 and hence also of the pinion 10 by means of which latter further movement is imparted to the slur drive rack 13. Each slur box 2 is consequently displaced an additional amount through the tie bar 3 to which it is connected. In this way a substantially constant overtravel of the slur cams is produced which achieves the required lead of the carriers ahead of the slur cams for the commencement of each carrier and slur cam traverse.

The linear differential in the illustrated example accordingly includes the displaceable slipper 56 and the chain sprocket 12 bodily movable to and fro by the mechanism LCM. This differential accordingly constitutes a means by which the two inputs derived from the variable differential mechanism VDM, i.e. the two pinions 5 and 12 (which are additive relatively to one another) are applied to influence the output in the form of the pinion 10 and the slur drive rack 13.

The sprockets 9 and 15 are driven by the shaft 6 through an overload or torque limiting device CD which in the illustrated example (see FIGS. 4, 5 and 6) is applied to an extension 6a of this shaft and is disposed adjacent to the pinion 5. As shown in FIG. 4, the device is housed in a casing 69 which is supported by a bracket 70 suitably attached to the framework of the machine. As will be seen more clearly in FIGS. 5 and 6, the torque limiting device, which is of known form, includes a hub 71 which is keyed and bolted to the shaft extension 6a. The pinion 5, and a driven plate 72 attached thereto by means of screws 73, are free to rotate about the hub 71 during disengagement. At 74 is indicated a drive plate which is keyed to and displaceable axially along the hub 71. Disposed between the drive plate 74 and the driven plate 72 is an intermediate, free running plate 75 which is suitably slotted as at 75a (FIG. 6) to retain, after disengagement, a plurality of balls 76 constituting the transmission link between the said drive and driven plates.

The opposed faces of the drive and driven plates are dimpled to provide seats for the balls 76, and the drive plate 74 is maintained in contact with the latter by means of a comparatively strong compression spring 77. The outer end of the hub 71 is externally screwthreaded to receive a complementarily internally threaded spring adjusting ring 78. The spring 77 surrounds the hub 71 and is interposed between the back of the drive plate 74 and the opposed annular face of the adjusting ring 78. Fixed to the driven plate 72, by the screws 73, is a cam plate 79 adapted to track the balls 76 after disengagement.

The principles of operation of the torque limiting device CD during normal running and on disengagement under overload conditions are as follows:

During normal running, with the hub 71 keyed on the drive shaft 6 as in FIG. 5, power is transmitted through the drive plate 74, keyed to the hub, and then through the medium of the balls 76 to the driven plate 72 (fixed to the pinion 5). The pressure of the spring 77 on the drive plate 74 ensures positive transmission.

'But any overload which occurs is transmitted to the pinion 5 and to the driven plate 72 attached thereto. When this overload exceeds the pre-set torque value, the balls 76 are rolled out of their seats thereby displacing the drive plate 74 along the hub 71 and against the spring 77 (see FIG. 6). The balls, now rolled out of their seats, are immediately tracked by the cam plate 79 attached to the driven plate 72 to a greater pitch circle than that of their seats, where they are retained by the freely rotating and tangentially slotted plate 75. In this condition of disengagement, the balls roll freely as in a thrust race and cannot accidentally re-seat. As and when required, reengagement is simply and speedily effected manually.

Preferably, and as shown, the drive plate 74 has rigidly combined therewith a flange '80 which, when the said plate is axially displaced along the hub 71, actuates a micro-switch 81 which is arranged to disconnect an appropriate circuit to stop the machine and also, if desired, to provide a visual or/and audible warning of overload.

If desired, two overload or torque limiting devices somewhat similar to that just described may be provided -0ne for each of the sprockets 9 and 15.

Instead of sprockets and chains forming part of the linear differential for imparting the additional movements to the slur cams as hereinbefore described, suitably toothed racks and pinions may alternatively be employed.

It has previously been stated that heretofore the tie bar has been driven an appreciable distance beyond the selvedge positions of the carriers and that because, in this case, the yarn carriers reach their stops while moving at a relatively high velocity, high impact forces limiting the maximum speed of the machine are developed. These unsatisfactory conditions are illustrated in the graphs constituting FIG. 7. Thus, in this figure, a yarn carrier is indicated at YC and a slur cam at SC. The slur cam is considered to be starting at A and moving to B, whereas the carrier starts at C and moves to D. The extent of slur cam travel is represented at SCT and of carrier travel at CT. Overtravel clue to draw cam is indicated at OT. The knitting width being considered is represented at KW. The common bottom line of the graphs is marked in degrees of rotation of the draw cam, in which connection it has to be borne in mind that this cam makes half of a revolution for each knitted course of the machine. The velocity curve of the draw cam is indicated at VC. The angle on the draw cam to obtain the lead is shown at EH. Increasing velocity of a slur cam and carrier across a knitting head is indicated by the upwardly pointing arrow at the left-hand side of FIG. 7, nil velocity being represented at 0. Thus, the velocity at which the slur and carrier drives start to move is represented at point B, whereas the velocity of these drives when carrier leaves a stop is indicated at point F. The point G represents the velocity of slur cam and carrier when the latter arrives at the relevant stop.

The corresponding graphs applicable to the improved machine equipped with a differential operated from a lead cam to achieve additional and substantially constant overtravel of slur cams are shown in FIG. 8. In these graphs, the additional travel imparted by the lead cam 68 to the slur cams SC, through the medium of the differential (7, 12, 56) is shown at AT. KW indicates the knitting width and hence also the carrier travel, whereas the carrier driver travel and slur cam travel due to the draw cam 16 is represented at CST. The velocity of carrier leaving relevant stop is represented at H and the velocity of this carrier reaching the stop at the opposite selvedge is represented at I.

The velocity of slur and carrier due to the draw cam 1-6 is shown on the curve SCV, and the velocity of slur due to lead cam 68 is shown at SV. The bottom line common to these graphs, is, as shown in FIG. 7, marked in degrees of rotation of the draw cam.

The variable draw mechanism associated with the differential of this invention may, if desired, be arranged to work in conjunction with light weight yarn carriers, the arrangement including carrier boxes which slide a small distance relative to drivers on a carrier rod, thereby permitting a small degree of lost motion at each terminal position and so avoiding the difficult engineering problem of the precise terminal positioning of heavy masses at high speed.

We claim:

'1. A straight-bar knitting machine comprising, in combination, a plurality of knitting heads at corresponding divisions of the machine; a sinker head at each division with sinkers for performing a yarn sinking function; slur cam boxes fiitted with sinker-operating slur cams, one to each division; a tie bar which extends along the length of the machine and couples the slur cam boxes together; at least one carrier rod which extends the length of the machine; yarn carriers at least one to each knitting head, mounted upon said carrier rod which latter is synchronously reciprocatable with the slur cams on all knitting widths but with a controlled lead of the said carriers over the slur cams; a slur drive rack combined with the said tie bar; carrier driving means for moving the carrier rod; a variable draw mechanism including a rotary draw cam, a fulcrummed main draw lever caused to swing by the cam and a draw bar movable to and fro from said lever; a gearing system adapted to convey from the draw mechanism reciprocating movements both to the carriers driving means and to the slur drive rack such as to impart to the yarn carriers and the slur cams traverses across the knitting and sinker heads, with the aforementioned lead of the carriers over the slur cams; left-hand and right-hand rotary selvedge screws at the ends of the machine for varying the traverses of the slur cams through the medium of the draw mechanism; nut housings axially movable along the selvedge screws, and stops movable together with the nut housings for limiting the traverses of the carrier rod; the machine being characterised in that the yarn carrier driving means are driven from the variable draw mechanism distances only slightly in excess of those required for carriers on the carrier rod to traverse the knitting width in either direction, and in that means are provided for imparting an extra linear movement to the tie bar each time the carrier rod is arrested by a stop thereby achieving the required lead of the carriers ahead of the slur cams.

2. A multi-head straight-bar knitting machine according to claim 1, wherein the carrier traverses are con trolled from the rotary draw cam included in the variable draw mechanism, so that the extent of each such traverse is a minimum and substantially constant amount in excess of the precise knitting width, and the said means employed to impart the extra linear movement to the tie bar each time the carrier rod is arrested by a stop consists of a differential arranged under the control of a secondary cam suitably timed in relation to the draw cam.

3. A multi-head straight-bar knitting machine according to claim 2, wherein the differential is a linear one adapted to be reciprocated to and fro under the control of the secondary cam.

4. A multi-head straight-bar knitting machine according to claim 2, wherein the secondary cam is a rotary lead cam which is rigidly secured to a half-speed shaft, and there are provided lead changeover means controlled by the said secondary cam so that the lead of the yarn carriers over the corresponding slur cams is automatically reversed at each reversal of the traverse of the slur cams across the sinker heads.

5. A multi-head straight-bar knitting machine according to claim 4, wherein the differential is a linear one including a chain sprocket which is engaged with a slur draw chain and is secured upon a shaft to which is also secured a pinion arranged in mesh with the slur rack, said shaft being mounted to turn in a guided slipper which is connected with and displaceable by the lead changeover means.

6. A multi-head straight-bar knitting machine according to claim 5, wherein idler sprockets free to rotate about axles set in the slipper are arranged to maintain engagement of the slur draw chain with the chain sprocket of the differential.

7. A multi-head straight-bar knitting machine according to claim 5, wherein the lead changeover means comprise a relatively long pivoted lever linked with the slipper, and a shorter pivoted lever, the said two levers being arranged parallel to one another and connected by a pitman which carries trucks arranged in contact with respectively opposite sides of the rotary lead cam.

8. A multi-head straight-bar knitting machine according to claim 5, wherein the carrier driving means are of the type including a chain furnished with a roller arranged to drive a carrier driving slide to and fro between two guided saddles having the carrier stops associated therewith, and wherein a shaft having secured thereon two sprockets around which are respectively 10 passed the carrier driving chain and the slur draw chain is oscillatable from a main rack driveable to and fro by the variable draw mechanism.

9. A multi-head straight-bar knitting machine according to claim 1, wherein at least one torque limiting device is incorporated in the transmission between the variable draw mechanism and the carrier and slur drives so that any malfunction or overload of the said mechanism will cause the device to disengage without damage to the machine.

10. A multi-llead straight-bar knitting machine according to claim 8, wherein the shaft having thereon the said two sprockets is oscillated from the main rack through the medium of a pinion in engagement therewith and there is associated with this pinion a torque limiting device so that any malfunction or overload will cause the device to disengage without damage to the machine.

References Cited UNITED STATES PATENTS 2,090,599 8/1937 Richter 66- 126 2,253,439 8/1941 MacKay 66-126 2,872,798 2/1959 Matthews et al 66126X MERVIN STEIN, Primary Examiner 

